Last spring, DBA conducted a construction phase load test program for a U.S. Army Corps of Engineers floodwall improvement project along the Missouri River in Kansas City, Kansas. Located on property owned and maintained by the Kansas City Board of Public Utilities (BPU), the BPU floodwall was slated for structural improvements including a series of buttresses founded on 24-in drilled shafts. As part of the project contract a load test program performed under the direction of a qualified P.E. and D.GE was required. General contractor L.G. Barcus & Sons, Inc., secured our Paul Axtell, P.E., D.GE as the qualified load test expert. DBA teamed up with load testing subcontractor Applied Foundation Testing, Inc., to perform the static load tests.
The load test program requirements included three test shafts, a statically loaded axial test shaft, a statically loaded lateral test shaft, and a combined statically loaded axial and lateral test shaft. The required combined lateral and axial test shaft provided some unique challenges with respect to applying the loads and collecting data. As can be seen in the picture above, the axial load was applied using dead weights.
We have added selected pictures from this unique project to our web albums, which can be viewed here.
Here is a blast from the past on pile groups: NCHRP Report 461 – Static and Dynamic Lateral Loading of Pile Groups. I had a request for this report recently, so I found it and figured we needed to post the links to it. Dan was the lead researcher on this report during his time at Auburn University, and had an all-star line up that included Dr. Mike O’Neill and Dr. Mike McVay, two of the heavy hitters in foundation engineering. The report introduction gives a good summary of the contents:
A key concern of bridge engineers is the design and performance of pile group foundations under lateral loading events,
such as ship or ice impacts and earthquakes. This report documents a research program in which the following were developed:
(1) a numerical model to simulate static and dynamic lateral loading of pile groups, including structural and soil hysteresis and energy dissipation through radiation; (2) an analytical soil model for nonlinear unit soil response against piles (i.e., p-y curves) for dynamic loading and simple factors (i.e., p-multipliers) to permit their use in modeling groups of piles; (3) experimental data obtained through static and dynamic testing of large-scale pile groups in various soil profiles; and (4) preliminary recommendations for expressions for p-y curves, damping factors, and p-multipliers for analysis of laterally loaded pile groups for design purposes. The report also describes experimental equipment for performing site-specific, static, and dynamic lateral load tests on pile groups.
Several full-scale field tests were conducted on pile groups of 6 to 12 piles, both bored and driven, in relatively soft cohesive and cohesionless soils. All of the groups were loaded laterally statically to relatively large deflections, and groups of instrumented pipe piles were also loaded dynamically to large deflections, equivalent to deflections that might be suffered in major ship impact and seismic events. Dynamic loading was provided by a series of impulses of increasing magnitude using a horizontally mounted Statnamic device.
For a relatively short (50 pages) report, there is a lot of information packed into it gleaned from a lot of full-scale field work.
Lateral Statnamic test, picture by David Graham of DBA, click here for a YouTube video
DBA has been selected by MnDOT as a geotechnical and load testing consultant for the design phase load test program and foundation design of a new bridge crossing the the St. Croix River near Oak Park Heights and Stillwater, Minnesota. The new bridge will carry State Highway 36 across the St. Croix River between Minnesota and Wisconsin. Currently, Highway 36 is carried on an 80-year old two-lane vertical lift bridge in downtown Stillwater. The new bridge will divert the heavy through traffic away from the historic downtown center and reduce travel time for commuters. The iconic lift bridge will be converted to a pedestrian and bicycle only structure.
Work began this summer on the load test program which consisted of one 8-foot test shaft, two 24-inch driven steel pipe piles, and two 42-inch driven steel pipe piles, all installed in the St. Croix River along the alignment of the new bridge. Local contractor Carl Bolander & Sons Co. was selected as the general contractor for the load testing program. Bolander self-performed the installation of the test piles and sub-contracted the construction of the test shaft to Case Foundation Company, of Chicago, Illinois. Axial load testing of the test shaft was performed by Loadtest, Inc., of Gainesville, Florida, using Osterberg Cells (O-cells). Dynamic testing of the driven piles using the pile driving analyzer (PDA) was performed by local geotechnical consultant Braun Intertec. Axial testing of the driven piles and lateral testing of the shaft and one of each size pile was performed using the Statnamic Device by Applied Foundation Testing, Inc. (AFT), of Jacksonville, Florida. DBA provided pre-test recommendations, assisted MnDOT in construction oversight, provided analysis and review of the test results, and made design recommendations based on the test results.
Following the successful load test program, DBA is working with MnDOT’s structural design consultants for the project, HDR, Inc. and Buckland & Taylor Ltd. to optimize the bridge design. Already, the design team has been able to lengthen the bridge spans and eliminate a river pier as a result of the load test results, as was recently reported by Minnesota Public Radio (MPR). Also, because the total number of drilled shafts required to support the main pier towers has been reduced, construction on the foundations will been moved up to 2013 rather than the original estimated start date in 2014, also reported by MPR.
Guideline for Interpretation of Nondestructive Integrity Testing of Augered Cast-in-Place and Drilled Displacement Piles
DFI Augered Cast-In-Place Pile Committee (2011-2012) Chaired by Michael Moran
Tracy Brettmann, Principal Author; Bernard Hertlein, Matthew Meyer, Bria Whitmire, Co-Authors
(Image from DFI)
This guideline provides practical guidance for the interpretation of nondestructive testing (NDT) of the integrity of augered cast-in-place (ACIP) and drilled displacement (DD) piles. … This guideline supplements DFI’s two primary publications on ACIP piles: Augered Cast-in-Place Pile Manual (2003) and the Inspector’s Guide for Augered Cast-in-Place Piles (2010). This guideline was developed to provide 1) more detailed explanations of the various test methods available, 2) guidance on interpretation of the results, and 3) some typical examples of the data and interpretation.
Seismic and Lateral Load Design and Testing Guidelines
DFI Seismic and Lateral Loads Committee (2011-2012)
Chaired by Mark Petersen and Zia Zafir (2003-2009)
Robert Kruger, Guideline Editor
This guidance document is intended to assist geotechnical engineers, pile designers, and contractors in analysis, design, and testing of piles and drilled shafts for lateral loads. … … This document discusses the background of different analytical and testing procedures and presents the recommended methods for analysis, design and testing of piles for lateral loads.
The paper describes a program of lateral load tests on six drilled shafts installed in a loess deposit at a site in Wyandotte County, Kansas. The lateral load test data, along with site characterization data that included CPT data, were used to develop a hyperbolic model to generate p-y curves for use in lateral load analyses in cemented soils. The model should be applicable to many “c-phi” soils (soils with both a cohesion intercept and a friction angle, such as cemented soils). Degradation of the static soil model to account for cyclic loading effects is included in the new model.
This paper was originally published in the DFI Journal,Vol. 5 No. 2, December 2011, the bi-annual Journal of the Deep Foundations Institute. DFI is an international technical association of firms and individuals involved in the deep foundations and related industry. The DFI Journal is provided to DFI members at no cost electronically or can be purchased in print at www.dfi.org.
This paper is one of several papers and articles published form a series of research projects by KU and the Kansas DOT. Some of the previous work can be found at these links:
Papers by Dan, Steve, and Tim that were included in the GeoFlorida 2010 conference have been uploaded to our Publications page. Dan and Steve co-authored a paper on the test program of the base grouted drilled shafts for the Audubon Bridge. Tim co-authored a paper with Willie NeSmith of Berkel and Company Contractors, Inc. on plate load testing of displacement grout columns. Dan was also a co-author with several others on a paper on jet grouting for improved pile lateral capacity.
One area of work we are frequently involved in is data analysis and evaluation of lateral load tests performed by the Statnamic testing device (learn more at the website of Applied Foundation Testing). The mathematics involved in the data reduction can be quite formidable as you interpret the dynamic load-response to an equivalent static load-response. Regardless of the math behind it, watching a test can be pretty cool. It is a whole lot of work for a brief moment of load, but in some situations it can be more economical than a traditional load test.
The video below is from a test on 170-foot long, 32-inch outside diameter steel pipe pile with 0.75"-inch wall thickness. The pile was filled with concrete that included an instrumented rebar cage.
Specialists in Deep Foundation Design, Construction, and Testing and Slope Stability Problems